Pneumocystis carinii pneumonia is an opportunistic infection that is common in immunosuppressed patients, including those receiving immunosuppressive therapy for inflammatory diseases. Wegener's granulomatosis is a rare disease characterized by the clinicopathologic features of upper and lower airway disease and renal disease demonstrating necrotizing granulomatous inflammation on histopathology. Immunosuppressive agents are a cornerstone of therapy for patients with Wegener's; combination therapy with glucocorticoids and cyclophosphamide leads to marked improvement in over 90% and complete remission in 75% of patients. Of 158 patients with Wegener's granulomatosis studied at NIH, there were 11 episodes of Pneumocystis carinii pneumonia. The purpose of this retrospective review of these 11 cases was to analyze the incidence of disease, the risk factors in this patient population, their clinical characteristics, and the treatment and outcome in these patients. Data were analyzed, a manuscript was submitted to the American Journal of Respiratory and Critical Care Medicine, and an article was published in the January 1995 issue of that journal (1995; 151: 795-799). This article defined a risk for a population of patients that is a major focus of NIAID research. The project took advantage of a population that could not be studied at other sites because Wegener's is so rare, and NIAID follows one of the largest cohorts in the world. Thus, this article focused on a unique NIH resource.